The formation of molded structures on substrates may find applications in many fields. In particular, it is desirable to form wafer level molded structures on semiconductor wafers, such as optics lens masters for electrooptical components. Such molded structures may include high aspect ratio or highly aspheric lenses or other optical components. Not only may these structures have high aspect ratios, but they may also require high surface quality.
In order to achieve these high aspect ratios and/or high surface quality, mold materials having high viscosities may be used. These high viscosity mold materials may achieve high aspect ratios without problems due to material flow and wet-out associated with lower viscosity materials. However, it may be difficult to achieve high surface quality with high viscosity mold materials.
One method to improve the surface quality of structures molded from high viscosity mold materials is to increase the pressure at which the structure is molded. This approach may have drawbacks, such as wear on the mold, as well as the possibility that such high pressure molding may damage the potentially fragile substrate on which the structure is molded.
Another method to improve these structures may be to use mold materials that have both a high viscosity and a high thixotropic index. Such materials may have the robustness to hold high aspect ratio forms until cured, and still may potentially be molded with high surface quality at lower pressures.
Embodiments of the present invention provide an approach that allows molding of structures on substrates using mold materials that may have low viscosities and/or low thixotropic indices.